Transducers are used in a wide variety of electronic applications. One type of transducer is known as a piezoelectric transducer. A piezoelectric transducer comprises a piezoelectric material disposed between electrodes. The application of a time-varying electrical signal will cause a mechanical vibration across the transducer; and the application of a time-varying mechanical signal will cause a time-varying electrical signal to be generated by the piezoelectric material of the transducer. One type of piezoelectric transducer may be based on bulk acoustic wave (BAW) resonators and film bulk acoustic resonators (FBARs). As is known, at least a part of the resonator device is suspended over a cavity in a substrate. This suspended area is usually referred as a membrane. As the membrane moves it translates a mechanical or acoustic perturbation to an electrical signal. In a similar manner, an electrical excitation is translated into an acoustical signal or a mechanical displacement.
Among other applications, piezoelectric transducers may be used to transmit or receive mechanical and electrical signals. These signals may be the transduction of acoustic signals, for example, and the transducers may be functioning as microphones (mics) and speakers and the detection or emission of ultrasonic waves. As the need to reduce the size of many components continues, the demand for reduced-size transducers continues to increase as well. This has lead to comparatively small transducers, which may be micromachined according to technologies such as micro-electromechanical systems (MEMS) technology, such as described in the related applications.
In many applications, there is a need to provide a transmit function or a receive function that comprises a comparatively high bandwidth transmitter, or receiver, or both. One application where higher bandwidth devices may be useful is in the transmission and reception of fast transition time signals. For example, an ideal square wave has an infinite slope at the leading a trailing edges of each signal. As should be appreciated by one skilled in the art, in the frequency domain such a signal comprises an infinite number of frequency components that are multiple of the fundamental frequency (harmonics). Realizable square waves have a large number of high frequency components with distributions around the harmonics. More complex signals have a frequency content that is not necessarily associated with harmonics. The frequency content of these higher complexity signals can be described by various types of mathematical decompositions such as Fourier, Laplace, Wavelet and others known to one of ordinary skill in the art. To transmit or receive these fast varying signals, the transmitter or receiver has to respond to the high frequency content. Thus, known transmitters and receivers require a high bandwidth to handle such signals.
While comparatively high bandwidth devices allow transmission and reception of signals have a broad range of frequencies, there are drawbacks to known broadband devices. For example, known high bandwidth devices are often more complex and more expensive to manufacture; they are more susceptible to noise limitations and often have a comparatively low quality (Q) factor, or simply Q. Thus, the gain of high bandwidth comes at the expense of price and performance.
What is needed, therefore, is an apparatus that overcomes at least the drawbacks of known transducers discussed above.